Thickened aqueous compositions

ABSTRACT

The invention relates to thickened aqueous compositions which comprise xanthan gum and a water-softening polymer.

[0001] The invention relates to thickened aqueous compositions whichcontain xanthan gum and at least one water softening agent.

[0002] Water softening products are sold commercially (such as theproduct Calgon®) and are used to aid detergency and prevent the build upof scale in the washing machine, such products are described in EP-A1-0628 627 (Benckiser), CH-577 937 (Lonza), WO-A1-95/21908 (Henkel) andEP-A2-0 622 449 (Huls).

[0003] The use of water-softening polymer polycarboxylates in detergentformulas has provided multiple benefits such as calcium sequestration,crystal growth inhibition to minimize encrustation on fabrics, lime soapdispersancy, and particulate soil dispersion. Sequestration of hardnessions such as calcium and magnesium by the polycarboxylates softens thewater and increases detergency. Also sequestration of hardness ions bythe polycarboxylates prevents the precipitation of salts of anionicsurfactants, which if allowed to occur will lead to reduced detergency.Dispersion of particulate soil such as clay by the polycarboxylatesprevents the redeposition of soils on the fabric. Such polymers are nowfound also in water-softening products.

[0004] Conveniently it would be preferred that water-softening productscould be added to the washing machine as a liquid rather than as a solidproduct. Also it is preferable that the product has a viscosity which isgreater than that of water.

[0005] We have found that aqueous compositions of water-softeningpolymers are difficult to thicken. In screening for an appropriategel/thickening system we found that many known systems were not stableor left residues on dark cloths after washing.

[0006] WO87/04143 describes a scale removal composition which comprisesan alpha-hydroxy carboxylic acid and, optionally, a Na silicate which isthickened with xanthan gum.

[0007] We have found that xanthan gum can form a thickened stable gelfor water softening agents which is stable and performs well.

[0008] Therefore we present as a feature of the invention an aqueousthickened composition comprising:

[0009] a) a water-softening agent which is a water-soluble polymer;

[0010] b) water; and

[0011] c) less than 1.0% wt of a xanthan gum.

[0012] Xanthan gum is an acidic, anionic, extracellularheterpolysaccharide, secreted from X. campestris. The polysaccharide isthought to act as a protective slime, essential for the pathogenecity ofthe micro-organism towards its plant host (Rutabaga plant) by blockingfluid flow through the xylem.

[0013] Xanthan gum is produced by bacterial fermentation and was thefirst polysaccharide produced on large scale using X. campestris. Such atechnique offers the advantage of reproducible physical and chemicalproperties, with a stable cost and supply. Nevertheless, unlike othermicrobial extracellular polysaccharides, the composition of the polymervaries with the Xanthomonas strain and culture conditions and in thepresence or absence of pyruvate and/or acetate substituents.

[0014] The polysaccharide forms highly viscous solutions at low polymerconcentrations, which are atypically insensitive to a wide range of saltconcentration, pH and temperature. In addition to this, Xanthansolutions exhibit strong shear thinning behaviour showing non-Newtonianbehaviour, a measurable yield stress from about 1% polymerconcentration, emulsion stabilising and particle suspending abilities,which are all indicative of intermolecular associations.

[0015] This natural polysaccharide is widely used in the food industryand to a lesser extent the pharmaceutical industry. Most of thecommercial Xanthan samples contain a variable amount of Na⁺, K⁺, Ca²⁺salts, and approximately 30-40% pyruvate content with 60-70% acetatecontent (although this is subject to variability).

[0016] The amount of the water-softening polymer is between 0.1 to 70%wt, ideally, 3 to 50% wt, preferably 15 to 35% wt. Ideally thewater-soluble polymer is only partly neutralised.

[0017] By the use of the phrase “a water-softening polymer” wepreferably mean polycarboxylate polymers, preferably polyacrylatepolymers, based on acrylic acid combined with or without other moieties.These include acrylic acid combined with; maleic acid (such as SokalanCP5 and CP7 supplied by BASF or Acusol 479N supplied by Rohm & Haas);methacrylic acid (such as Colloid 226/35 supplied by Rhone-Poulenc),phosphonate (such as Casi 773 supplied by Buckman Laboratories), maleicacid and vinyl acetate (such as polymers supplied by Huls), acrylamide,sulfophenol methallyl ether (such as Aquatreat AR 540 supplied by Alco),2-acrylamido-2-methylpropane sulfonic acid (such as Acumer 3100 suppliedby Rohm & Haas or such as K-775 supplied by Goodrich),2-acrylamido-2-methylpropane sulfonic acid and sodium styrene sulfonate(such as K-798 supplied by Goodrich), methyl methacrylate, sodiummethallyl sulfonate and sulfophenol methallyl ether (such as Alcoperse240 supplied by Alco), polymaleates (such as Belclene 200 supplied byFMC), polymethacrylates (such as Tamol 850 from Rohm & Haas),polyaspartates, ethylenediamine disuccinate and organo polyphosphonicacids and their salts such as the sodium salts ofaminotri(methylenephosphonic acid) and ethane 1-hydroxy-1,1-diphosphonicacid.

[0018] Preferably the polymer is polyacrylic acid, blended with orwithout a polymaleic acid polymer, or a polyacrylic/polymaleic acidcopolymer (such as those sold by BASF under the Sokalan trademark).

[0019] The term “partly neutralised” excludes neutralisation of morethan 90% of the free carboxyl groups.

[0020] Preferably the average MW (Mw) of the polymer should be greaterthan 1,000, ideally greater than 2,000, based upon the free acid.

[0021] Additional water-softening agents may be added to thecomposition. Preferably the additional water softening agent is awater-soluble water softening agent, which is organic or inorganic.Inorganic water-soluble water softening agents that may be presentinclude alkali metal (generally sodium) carbonate; while organicwater-soluble water softening agent which may be present; monomericpolycarboxylates (such as citrates, gluconates, oxydisuccinates,glycerol mono-di- and trisuccinates, carboxymethyloxysuccinates,carboxymethyloxymalonates, dipicolinates andhydroxyethyliminodiacetates); sequestering agents (such as phosphonatesand iminodisuccinates); radical scavengers (such as BHT); phosphonates(such as diethylenetriaminepenta (methylene phosphonic acid) and itscorresponding pentasodium salt, (available under the trade names Dequest2060 and Dequest 2066 Monsanto Chemical Co.), DTPMP and DTPMA).

[0022] The remaining part of the formulating can be water, with up to95% w/w of the formulation being water, ideally deionised water.

[0023] The presence of surfactant is not excluded from this invention.This invention may find use in the preparation of thickened detergentliquid compositions which contain a water-softening polymer. Preferablythe composition contains less than 5% wt, ideally less than 1% wt, of asurfactant.

[0024] Organic solvents may optionally be added but are not essential inthe present invention and can be any water-miscible organic solvent.Suitable solvents include C3-C12 alkyl glycol ethers and C1-C4alcohols,such as methanol, ethanol and isopropanol. More preferably, the solventis selected from the group consisting of EGBE, ethylene glycol hexylether (“EGHE”) and mixtures thereof. The solvent is typically present inan amount from about 0.5% to about 4.0%, preferably from about 0.75% toabout 2.5%, and most preferably from about 1.0% to about 2.0% by weightof the composition. EGBE is available from Union Carbide under the tradename Butyl Cellosolve. EGHE is available under the trade name HexylCellosolve from Union Carbide.

[0025] The pH, as defined in the present context, is measured in theneat compositions at 20° C. For optimum stability of these compositions,the neat pH, measured in the above-mentioned conditions, must be in therange of from 3 to 7, ideally from 4 to 6, especially 5.1 to 5.7. The pHof these compositions herein can be regulated by the addition of aBronsted acid or base.

[0026] Xanthan gum is a water-soluble polymer. It is soluble in hot andcold water, as well as being stable in acidic and alkaline conditions(pH 1.5-13). The solubility of Xanthan gum allows highly viscoussolutions at low concentrations, i.e., a 1% solution has a viscosity of800-10000 cps (60 rpm/LVF Brookfield viscometer). Preferred viscositiesof solutions generated are 30 to 3000 cps, preferably 500 to 2000 cps,ideally 1000 to 1500 cps, (measured with a Brookfield LVF, spindle 2, 12rpm @ 20° C.).

[0027] Preferred concentrations of xanthan gum are less than 1.00% wt,ideally less than 0.7% wt, preferably less than 0.5% wt, and especiallyless than 0.4% wt. A preferred source of xanthan gum is Rhodopol T, CASREG Nr. 11138-66-2 (company Rhodia).

[0028] A preservative may be added as are commonly found in the field,such as 1-(3-Chloroallyl)-3,5,7-triaza-1-azoniaadamantane-chloride (CASREG Nr. 004080-31-3), available as Dowcill 75, at up to 0.1% wt.

[0029] An alternative feature of the invention is a method of softeningwater in a fabric washing machine which method comprises the addition ofa composition as defined herein above. Preferably the hardness of thewater used in the fabric washing machine is greater than 100 ppm,ideally greater than 150 ppm.

[0030] An alternative feature of the invention is the use of xanthan gumin thickening an aqueous composition comprising a water-softeningpolycarboxylate polymer.

Stability

[0031] Initial viscosity: 1000-1400 cps (measured with a Brookfield LVF,spindle 2, 12 rpm @ 20° C.)

[0032] The system was stable over a period of 3 months over a range ofdifferent conditions.

EXAMPLE

[0033] As 100% actives Dehardened Sterilized to 100% Water SodiumCitrate 10-20 Water softening  2-10 polymer Xanthan gum 0.1-1.0Preservative -   0-0.1 optional Dye - optional   0-0.1 Perfume -optional   0-0.8

1. An aqueous thickened composition comprising: a) water-softening agentwhich is a water-soluble polymer; b) less than 1% wt of a surfactant; c)water; and d) less than 1.0% wt of a xanthan gum.
 2. A thickenedcomposition according to claim 1 comprising 0.1 to 70% wt of awater-softening polyacrylate.
 3. A thickened composition according toclaim 2 comprising 3 to 50% wt of a water-softening polycarboxylatepolymer.
 4. A thickened composition according to claim 1 wherein thewater-softening polycarboxylate polymer is a polymer based on acrylicacid combined with or without other moieties.
 5. A thickened compositionaccording to claim 4 wherein the water-softening polycarboxylate polymeris an acrylic/maleic copolymer.
 6. A thickened composition according toclaim 1 which additionally comprises citric acid or a salt thereof.
 7. Athickened composition according to claim 1 which additionally comprisesa phosphonate.
 8. A thickened composition according to claim 1 aswherein the pH of the neat composition is from 3 to 7, measured at 20°C.
 9. A thickened composition according to claim 1 comprising less than0.4% wt of a xanthan gum.
 10. Use of xanthan gum in thickening anaqueous composition comprising a water-soluble water-softening polymer.11. A method of softening water in a fabric washing machine which methodcomprises the addition of a composition according to claim
 1. 12. Athickened composition according to claim 2 comprising 0.1 to 70% wt of apolycarboxylate polymer.